[all-commits] [llvm/llvm-project] 3ff07f: [SLP] Allow reordering of vectorization trees with...

[Alexey Bataev via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 3ff07fcd542ebef657bb93fe8ee1750527210b94
      https://github.com/llvm/llvm-project/commit/3ff07fcd542ebef657bb93fe8ee1750527210b94
  Author: Alexey Bataev <a.bataev at hotmail.com>
  Date:   2020-09-21 (Mon, 21 Sep 2020)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    M llvm/test/Transforms/SLPVectorizer/X86/jumbled_store_crash.ll
    M llvm/test/Transforms/SLPVectorizer/X86/reorder_repeated_ops.ll
    M llvm/test/Transforms/SLPVectorizer/X86/vectorize-reorder-reuse.ll

  Log Message:
  -----------
  [SLP] Allow reordering of vectorization trees with reused instructions.

If some leaves have the same instructions to be vectorized, we may
incorrectly evaluate the best order for the root node (it is built for the
vector of instructions without repeated instructions and, thus, has less
elements than the root node). In this case we just can not try to reorder
the tree + we may calculate the wrong number of nodes that requre the
same reordering.
For example, if the root node is \<a+b, a+c, a+d, f+e\>, then the leaves
are \<a, a, a, f\> and \<b, c, d, e\>. When we try to vectorize the first
leaf, it will be shrink to \<a, b\>. If instructions in this leaf should
be reordered, the best order will be \<1, 0\>. We need to extend this
order for the root node. For the root node this order should look like
\<3, 0, 1, 2\>. This patch allows extension of the orders of the nodes
with the reused instructions.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D45263